The present invention relates to nuclear magnetic resonance (NMR) spectroscopy and, more particularly, to novel methods of, and apparatus for, decoupling a first coupled nuclear species from the magnetic resonance response signals from a second desired species, and especially for providing at least one, or several (if applicable), of decoupling and/or nuclear Overhauser enhancement and/or selective saturation (in saturation transfer experiments) with in vivo spectroscopic imaging.
It is now relatively well known, among those skilled in the medical diagnostic imaging arts, than carbon-13 (.sup.13 C) nuclear magnetic resonance spectroscopy may offer promise as a technique for the study of human metabolic processes in vivo. However, .sup.13 C in vivo spectroscopy is, even if the proper high-field magnetic system is provided with the necessary spatial and temporal stability for spectroscopic imaging, not without difficulties; .sup.13 C is a low-abundance and low-sensitivity nucleus, and acquiring spectra therefrom with adequate signal-to-noise ratio is relatively difficult. The acquisition of suitable .sup.13 C spectra is often further complicated by the spectral line splitting resulting from dipolar interactions between the .sup.13 C nuclei and the .sup.1 H nuclei (protons). Minimization of spectral line splitting by spin decoupling techniques, wherein the sample is irradiated over the proton chemical shift spectrum at the same time as the .sup.13 C experiment is being carried out, was proposed by F. Bloch, in "Recent Developments in Nuclear Induction", Phys. Rev. 93, 944 (1955). The spin decoupling technique effectively saturates the proton .sup.13 C spectra; this collapse of the multiplet structure results in a more easily interpreted spectrum while also improving the signal-to-noise ratio by concentrating all of the signal of the multiplet in a single spectral line.